Verdigris and PVC: Saving Southern So-Called Dollars Mega Thread from Environmental Damage

Improper Storage Is the Enemy of Numismatics

Improper storage is the enemy of numismatics. I mean that literally. I have examined hundreds of Southern so-called dollars, exposition medals, and store cards over the years. The greatest threat is not circulation. It is not age. It is not even a weak strike. It is the environment these pieces have lived in for the last 50, 100, or 140 years.

The Southern So-Called Dollars Mega Thread is a perfect case study. It has grown into a long-term discussion of medals from Southern Expositions from the 1870s to the 1900s. These are not ordinary coins. They are privately struck exonumia — so-called dollars, medals, fobs, and store cards issued to promote Louisville, Atlanta, New Orleans, Raleigh, Winston-Salem, Jamestown, and a dozen other cities determined to announce a New South after Reconstruction. Many were struck in bronze, white metal, and silver by Northern die sinkers and medallic firms for Southern promoters. That geographic irony matters. The pieces were sold in humid Southern climates. They were stored in Southern homes. And they were often kept in the very materials that accelerate decay.

In my experience grading and conserving exonumia, I see the same pattern repeated. A rare HK-791A. A beautiful SH 3-61 by Charles Theiler of Cincinnati. Or a bronze SH 3-62 by Edward A. Kretschman for the William Warner & Brother Company of Philadelphia. Each one arrives with a strong provenance story. Then I look closer. A pale green spot. A powdery pit. A sticky green film. Left untreated, it will eat through the design. My job is not to make a damaged piece look new. My job is to stabilize it. I stop active corrosion. I preserve every micron of original surface and historical evidence. This guide shows how I do that. It also shows how you can spot the danger before you buy, sell, or store your own Southern exposition pieces.

Why Southern Exposition Medals Are Uniquely Vulnerable

To understand environmental damage, you must first understand what these medals are made of and where they lived. The Shevlin & Hyder catalog of so-called dollars lists dozens of Southern issues. But the forum thread reminds us that many were not struck at the United States Mint. They were struck by private firms like William H. Warner & Brother Co. of Philadelphia. They were struck by Cincinnati die sinkers like Charles Theiler. And they were struck by Philadelphia sculptors like Kretschman, whose initials EAK appear on numerous 1880s medals.

That private origin means inconsistent alloys. In my experience, I have examined:

• Bronze medals – including the William Warner & Brother bronze medal that started the thread, SH 3-62, the 1884 North Carolina Exposition medal, the 1884 Portsmouth, VA Confederate reunion piece, and the 1900 Winston-Salem piece, typically 32-33 mm. Bronze is beautiful. It has wonderful eye appeal when the patina is right. But it is chemically reactive.
• White metal pieces – such as Rulau-Ky-Lo-32 for the 1883 Southern Exposition, often a tin-lead alloy. White metal is soft. It is porous. It is prone to oxidation and surface bloom.
• Silver store cards and medals – including the fabulous silver store card of William Warner and Brother Co. resold by Steve Hayden in 2025 after the 2020 Stacks sale of the E Pluribus Unum Collection. Silver does not suffer bronze disease. But it suffers sulfur toning and PVC damage just as severely.
• Large-format exposition medals – such as HK-142 for the 1884-1885 World’s Industrial and Cotton Centennial Exposition in New Orleans, engraved by George Morgan of the U.S. Mint using David Yates’ symbolism from the 1876 Philadelphia exposition, and the 1887 Piedmont Exposition medal with President Grover Cleveland. These were often sold as souvenirs. They were kept in drawers, attics, and humid display cases.

Add to that the Southern environment itself. Louisville in 1872 and 1883. Atlanta in 1881 and 1887. New Orleans in 1884. Jamestown in 1907. These are not dry climates. For more than a century, collectors in those regions stored medals in wooden cabinets, leatherette albums, and soft vinyl flips. Humidity cycles from 30% in winter to 85% in summer. Airborne chlorides from coastal air. Sulfur from coal smoke and later from cardboard and wood. It creates a perfect laboratory for corrosion.

I have seen more environmental damage on Southern so-called dollars than on comparable Northern issues from the same period. Not because the medals were inferior. Because of where they were loved and kept.

Bronze Disease: The Active, Powdery Killer of Warner and Kretschman Bronzes

If there is one term every bronze so-called dollar collector must learn, it is bronze disease. I treat this as a conservation emergency. Not a cosmetic flaw.

What Bronze Disease Is Chemically

Bronze is primarily copper and tin. When it is stored in the presence of chlorides — from salt air, from PVC holders, from a collector’s fingerprints, from old cleaning chemicals — copper forms copper chloride. In the presence of moisture and oxygen, that copper chloride hydrolyzes to form nantokite, cuprous chloride, and then atacamite and paratacamite. Those are bright, powdery, pale green to turquoise copper hydroxychlorides. The reaction releases hydrochloric acid. That acid attacks more copper. That creates more chloride. That creates more acid. It is a self-perpetuating cycle.

On a medal, you will see it as a small, pale, powdery spot. It often sits in a recessed area of the design, along the rim, or under a letter. It looks like mold. It feels like powder. Under magnification, it is crystalline and rough. Unlike a stable patina, it is active. It will pit the surface underneath it. Eventually it creates a deep, crater-like hole that destroys lettering, dates, and mint marks.

How I Identify It on Southern Medals

In my experience grading, I look for bronze disease in the protected areas where moisture collects. Between the letters of Wm H. Warner & Brother. In the scrollwork on the reverse of the 1900 Winston-Salem medal. In the cotton bolls on the obverse of the 1881 Atlanta International Cotton Exposition medal by Theiler. And around the beehive on its reverse. A stable, dark brown or olive patina that is smooth and adherent is not bronze disease. A light green, powdery, raised spot that spreads is.

Collectors often confuse bronze disease with simple verdigris. Verdigris is a general term for green corrosion products, often copper carbonate, which can be stable. Bronze disease is specific. It is active. It is chloride-driven. The distinction matters. Verdigris may be left alone. Bronze disease must be treated immediately or the piece will be lost.

I have examined bronze HK-761s and SH 3-62s where a spot the size of a pinhead in 2015 had become a 3 mm pit by 2020. It completely obscured Kretschman’s EAK signature. The owner thought it was toning. It was not. It was chemistry.

Actionable Takeaways for Buyers

• Never buy a bronze Southern medal with a powdery pale green spot without asking if it has been stabilized. If the seller cannot answer, assume it is active.
• Do not put a bronze medal with suspected bronze disease into a sealed flip with other medals. The moisture and chlorides can spread.
• Photograph the spot with scale and date it. Active spots grow. Stable spots do not.

PVC Plasticizer Damage: The Green Slime in the Flip

Bronze disease gets the headlines. But in my conservation practice, PVC damage is the most common and most preventable form of environmental damage I see on Southern so-called dollars from the 1960s through the 1990s.

What PVC Does to Metal

For decades, collectors stored coins and medals in soft vinyl flips, vinyl pages, and plastic albums. Those materials contain polyvinyl chloride. Over time, especially in heat and humidity — exactly the conditions of a Southern attic or garage — the plasticizer migrates out of the vinyl. That plasticizer is a chlorinated compound. It breaks down. It releases chlorine and hydrochloric acid. It reacts with copper in bronze to form green copper chloride. It reacts with silver to form green and black silver chloride and sulfide spots.

On silver Warner store cards, PVC damage often appears as a sticky, bright green spot with a halo. Or as a network of green lines that follow the contact points of the flip. On bronze, it accelerates bronze disease. On white metal, it creates a dull, pitted, gray-green bloom that cannot be removed without loss of surface.

How I Have Seen It Ruin Rare Pieces

I recall examining a white metal 1883 Southern Exposition piece, Rulau-Ky-Lo-32, that had been in the same vinyl flip since the 1970s. The obverse Liberty Head was perfect. But the reverse, where the medal had rested against the plastic for decades, was covered in a fine green powder. The plastic had literally printed itself onto the medal. The same happens with the 1872 Louisville Industrial Expo medal, possibly by Theiler, with the T&C mark at 4:00 on the reverse. If that medal spent 40 years in vinyl, the recesses will tell the story.

PVC damage is also insidious because it is contagious in a storage box. One medal off-gassing in a closed box will damage its neighbors. I have opened boxes where five consecutive Southern medals were all spotted because the middle one was in a bad flip.

How to Spot It

1. Look for bright, almost neon green spots that are perfectly round where the flip touched the medal.
2. Look for a sticky or tacky feel on the surface, or a chemical smell when you open the holder.
3. Look for yellowing or stiffening of the flip itself — a sign the plasticizer has left the plastic and gone onto your medal.
4. Check the edges and rim, where the medal pressed against the seam of the flip.

Actionable takeaway: If you see PVC damage, remove the medal from the flip immediately. Do not re-holder it in vinyl. Do not attempt to wipe it with a cloth. Wiping spreads the chlorides. It needs a proper solvent treatment, which I will discuss below.

Oxidation, Toning, and Humidity: When Color Is Good and When It Is Not

Not all color is damage. As a conservator, I spend as much time protecting original toning as I do treating corrosion. But I must teach collectors to distinguish between desirable patina and destructive oxidation.

Stable Toning vs. Active Oxidation

On a silver 1884 New Orleans Cotton Expo medal or a silver Warner store card, a deep amber, russet, or even blue-gray toning that is smooth, even, and adherent is often original and desirable. It formed slowly over decades in a stable environment. It actually protects the surface. On bronze, a dark chocolate brown patina with no powder is also stable and valuable. That kind of patina is a key part of eye appeal and numismatic value.

Active oxidation is different. It is rough. It is powdery, flaking, or pitting. On white metal, oxidation appears as a dull white or gray bloom that feels chalky. On bronze, it appears as brown, black, or green crusts that are raised and fragile. On silver, sulfur oxidation from cardboard, wood, or rubber bands creates black or dark brown spots. Those spots are often accompanied by a rotten-egg smell in the storage container.

In the Southern context, humidity is the driver. I have examined medals from the 1887 Piedmont Exposition in Atlanta and the 1907 Jamestown Exposition, SH 15-2, that were stored in Piedmont Park-area homes with no climate control. The summer humidity allowed oxidation to proceed in cycles. Wet in July. Dry in January. Wet again. Each cycle expands the corrosion products. It lifts the surface. It creates a rough, porous layer that then traps more moisture.

The Role of Handling and Storage Materials

I have seen oxidation accelerated by:

• Paper envelopes and cardboard 2x2s that contain sulfur and lignin
• Wooden cabinets that off-gas acids
• Leatherette albums with tanned leather
• Rubber bands, which are pure sulfur
• Fingerprints, which deposit salts and oils, especially on bronze

For Southern medals, which often have high relief — think of Hebe, the Greek goddess of Youth, on the 1872 Louisville medal, or the exposition building on the 1881 Atlanta medal — the high points are handled. The low points trap moisture. That is why damage so often starts in the fields and lettering.

Actionable takeaway for sellers: Do not describe a medal as “original toning” if the color is powdery, uneven, or accompanied by pitting. Buyers who know conservation will spot the difference under magnification. And misrepresentation destroys trust in this specialized market.

Proper Chemical Conservation: Acetone Dips and Stabilization Protocols

This is the section where I must be both authoritative and responsible. As a professional conservator, I use chemical conservation. But I do not recommend that beginners experiment on rare Southern so-called dollars. What I can do is explain the principles I use. That way you understand what proper treatment looks like. And you learn what dangerous folk remedies to avoid.

The Acetone Dip: Removing PVC and Surface Contaminants

Acetone is a polar solvent that dissolves PVC plasticizer, oils, and many organic contaminants without attacking the metal itself. In my practice, a medal will be rinsed in pure acetone — never nail polish remover, which contains oils and fragrances — in a glass container, often for a few minutes. Then it is rinsed in a second bath of clean acetone. Then it is air-dried on a clean, lint-free surface. For PVC damage, this can dissolve the sticky green film and stop further reaction.

Acetone does not remove bronze disease. It does not remove stable patina. It is a cleaning step, not a cure. After an acetone dip, I examine the medal under magnification. If PVC residue remains in recesses, I may use a soft brush with acetone. If bronze disease is present, a different protocol is required.

Stabilizing Bronze Disease

True bronze disease treatment is beyond a simple dip. In a professional lab, I would first remove loose corrosion mechanically under magnification. Then I would treat the pit with a chloride-removing solution, often involving distilled water soaks and, in advanced cases, a corrosion inhibitor such as benzotriazole. The goal is to convert the active chlorides to a stable form and seal the pit. This is delicate work. Done incorrectly, it can strip patina. It can pit the surface further. It can leave chemical residues that cause new damage.

What I will say to collectors is this: a medal with active bronze disease that receives no treatment will continue to deteriorate. A medal that receives an amateur treatment with lemon juice, vinegar, baking soda, olive oil, or commercial coin dip will almost certainly be ruined permanently. I have seen all of those folk remedies attempted on Southern bronzes. In every case, the original surface was lost.

What Never To Do

• Never polish. Polishing removes patina, softens detail, and destroys value.
• Never use olive oil or other oils. They trap moisture and chlorides against the surface.
• Never use lemon juice, vinegar, or salt. They introduce more chlorides and acids.
• Never use baking soda paste. It is abrasive and alkaline.
• Never use ultrasonic cleaners without training. They can drive corrosion deeper into pits.
• Never heat a medal to dry it. Heat can accelerate reactions.

Actionable takeaway: If you suspect bronze disease or PVC damage on a rare piece like HK-791A, HK-761, or a Warner bronze, your best action is to isolate it. Keep it dry. And consult a professional conservator or a reputable third-party grading service that offers conservation. Document the damage with photos before any treatment.

Storage Best Practices I Recommend for Southern Exposition Collections

Prevention is cheaper, safer, and more effective than any chemical treatment. In my experience grading collections, the collectors who preserve their Southern medals best share the same habits.

The Ideal Environment

I recommend storage at 35-45% relative humidity, stable temperature, and in the dark. For most collectors, that means an interior room, not an attic, garage, or exterior closet. A small dehumidifier or silica gel packs in a sealed cabinet can maintain that range even in Louisiana or Georgia. I check my own storage with a hygrometer weekly.

The Ideal Holders

1. Mylar or polypropylene flips and sleeves – inert, crystal clear, and free of plasticizers. These are the gold standard.
2. Archival paper envelopes – acid-free, lignin-free, for white metal and bronze that needs to breathe slightly.
3. Custom trays with inert foam – for display, with no vinyl, no rubber, no wood contact.
4. Slabs from reputable grading services – if the medal has been conserved and slabbed, keep it slabbed. The sealed environment is protective.

Never use soft vinyl flips, PVC pages, cardboard 2x2s with sulfur, or leather albums for bronze or silver Southern medals. I know this sounds strict. But I have seen the damage those materials cause firsthand.

Handling Protocol

I always handle medals with clean, dry cotton or nitrile gloves, by the edges, over a padded surface. I never touch the fields. After handling, I return the medal to its holder immediately. Fingerprints on bronze are not just unsightly. They are a source of chlorides that can start bronze disease years later.

Case Studies from the Mega Thread: What I Would Look For

Let me apply these principles to the specific pieces discussed in the thread. Because this is where theory meets real collecting.

The William Warner & Brother Bronze Medal

The bronze medal that opened the thread, described as a “SCD key” with a strong price in May 2025, connects Philadelphia with Southern themes. As a conservator, my first questions would be: Is the bronze patina stable and dark? Are there any pale green spots in the lettering? Has it been in a vinyl flip? A Warner bronze with original, uncleaned patina and no active corrosion is a premium piece. It has far greater collectibility and numismatic value. The same medal with a treated bronze disease pit will grade lower and sell for less, no matter how rare the type.

SH 3-61, SH 3-62, and SH 3-63: The 1883 Southern Exposition Trio

The 1883 Southern Exposition in Louisville, from 1883 to 1887 in Old Louisville, featured Edison’s light bulb and the upcoming Statue of Liberty. Theiler’s SH 3-61 and Kretschman’s SH 3-62 in bronze are prized. On SH 3-62, I would examine the Liberty Head obverse and the EAK reverse under magnification for powdery spots in the hair and drapery. Kretschman’s lettering style is distinctive. And bronze disease loves lettering. A clean example with sharp, uncorroded letters is worth far more than a pitted one. A true rare variety in mint condition will show original luster and a strong strike.

HK-142 and the New Orleans Cotton Expo Medals

George Morgan’s HK-142 for the 1884-1885 New Orleans exposition is a major medal. In silver, I would look for PVC halos. In bronze, I would look for bronze disease in the cotton and industrial symbols. The 13 SCD medals from this exposition are difficult to find, as the thread notes. And environmental damage is a major reason why so many are in poor condition. A well-preserved example is a true rarity.

HK-761 and the Jamestown SH 15-2 Fob

The bronze HK-761 from the Jesinger collection, described as a great rarity, and the 1907 Jamestown SH 15-2 fob, are both bronze pieces from coastal Virginia. Coastal storage means chlorides. I would expect a conservator to check these pieces first for bronze disease, even if they look perfect to the naked eye. The Great White Fleet theme of Jamestown makes these medals desirable to naval collectors. But naval collectors are also savvy about corrosion.

Across all these case studies, the pattern is clear: rarity does not protect a medal from chemistry. In fact, rare medals are often stored longer in bad holders because they are “special” and put away.

Conclusion: Collectibility, Historical Importance, and the Conservator’s Promise

Southern so-called dollars and exposition medals are more than collectibles. They are primary sources for the story of Reconstruction, the New South, and American industrialization. The 1872 Louisville Industrial Expo before the Panic of 1873. The 1881 Atlanta Cotton Exposition with its working cotton mill at Oglethorpe Park. The 1883 Southern Exposition. The 1884 North Carolina Exposition in Raleigh that led to NC State University. The 1887 Piedmont Exposition with President Cleveland. And the 1907 Jamestown Exposition celebrating 300 years of English settlement. Each medal is a tiny monument to a region trying to rebuild and rejoin the nation.

That historical importance is exactly why environmental damage matters. When bronze disease pits through the name of Charles Theiler or Edward A. Kretschman, when PVC obscures the beehive symbol of industry and harmony on the Atlanta medal, when oxidation erases Hebe or the exposition building, we lose historical evidence that cannot be recreated. The die sinkers are gone. The exposition buildings are gone. The medals remain, if we care for them.

In my experience, the collectors who build the best Southern collections are not just buyers, but stewards. They learn to spot verdigris. They learn to recognize PVC. They keep humidity low. And they seek professional conservation when needed. They understand that an acetone dip, properly done, can save a medal from a bad flip. But prevention — inert holders, stable environment, careful handling — is the true conservation.

Improper storage is the enemy of numismatics, but knowledge is its antidote. Identify the signs early. Act conservatively. And never let a powdery green spot go untreated. Your Southern so-called dollars, from Warner’s Philadelphia bronzes to Morgan’s New Orleans medals, have survived more than a century of Southern summers. With proper care, they will survive another century in your collection, and in the collections of those who come after you.

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